Diode Bridge Rectifier Circuit Tutorial

In this post, we will refresh about the construction, Operation, Equations for output voltage and current, Advantages of the Bridge type rectifier. In this post we will discuss about only diode based bridge testifiers.

When the bridge rectifier circuit consists of only diodes it is called as Uncontrolled Bridge Rectifier. Because the output of the circuit can not be varied.

When the bridge rectifier circuit consists of two diodes and two SCRs it is called as Semi-controlled Bridge Rectifier.

When the bridge rectifier circuit consists of four SCRs it is called as fully controlled Bridge Rectifier.

Diode Bridge Rectifier Operation:

The Bridge Rectifier has four diodes connected to form a bridge as shown in the following figure.

The AC input voltage is applied to the diagonally opposite ends of the bridge. The load is connected between the other two ends of the bridge.

For the positive half cycle of the input AC voltage, diode D1 and D3 conduct. But Diodes D2 and D4 do not conduct.

The conducting diodes will be in series with the load. As the circuit is closed, current flows through the load.

During negative half cycle of the input AC voltage, diodes D2 and D4 will conduct. But diodes D1 and D3 will not conduct.

The conducting diodes(D2 and D4) will be in series through the load.

As the circuit is closed, current flows through the load.

Thus the AC waveform(bidirectional wave) is converted into DC waveform.

Full wave Diode Bridge rectifier waveforms

Diode Bridge rectifier Equations:

VDC = 2Vm/π

IDC = VDC/R = 2Vm/(πR) = 2Im/π

Diode Bridge Rectifier Advantages :
Compared to the centre tapped full wave rectifier circuit the bridge rectifier circuit has the following advantages:

The bridge rectifier has the maximum efficiency of 81.2% and the ripple factor is 0.48. This is similar to that of centre tapped circuit.

The peak inverse voltage across either of the non conducting diodes is equal to the peak value of the transformer secondary voltage Vm. This PIV is just half of the centre tapped rectifier circuit(2Vm). So the PIV rating required for the diodes in the bridge rectifier is only half of that for a centre tapped full-wave rectifier.

The bulky center tapped transformer is not required. The transformer utilisation factor is considerably high.

Diode Bridge Rectifier Disadvantages:

The bridge rectifier circuit requires four diodes compared to the two diodes of the centre-tapped full wave rectifier.